1. What does it mean?
개인팬 means an individual-member or solo fan. The focus is a particular member's performances, projects, or personality rather than the group as a whole. It does not, by itself, say anything about hostility toward the other members.
Also written or said as gaeinpaen
2. The nuance
Do not treat 개인팬 and 악개 as synonyms. The latter specifically criticizes antagonistic behavior, whereas having one main interest can be entirely harmless.
3. Examples
“나는 그 배우 활동을 보고 개인팬이 됐어.”
I became a fan of that particular member through their acting work.
“개인팬이어도 다른 멤버를 존중해야지.”
Even if you follow just one member, you should respect the others.
Sources
References support the meaning and usage. Example sentences are written for NoCapWiki.